The polyphenylene ether resins are a family of engineering thermoplastics that are well known to the polymer art. These polymers may be made by a variety of catalytic and non-catalytic processes from the corresponding phenols or reactive derivatives thereof. By way of illustration, certain of the polyphenylene ethers are disclosed in Hay, U.S. Pat. Nos. 3,306,874 and 3,306,875, and in Stamatoff, U.S. Pat. Nos. 3,257,357 and 3,256,358. In the Hay patents, the polyphenylene ethers are prepared by an oxidative coupling reaction comprising passing any oxygen-containing gas through a reaction solution of a phenol and a metal-amine complex catalyst. Other disclosures relating to processes for preparing polyphenylene ethers resins, including graft copolymers of polyphenylene ethers with styrene type compounds, are found in Fox, U.S. Pat. No. 3,356,761; Sumitomo, U.K. Pat. No. 1,291,609; Bussink et al., U.S. Pat. No. 3,337,892; Blanchard et al., U.S. Pat. No. 3,219,626; Laakso et al., U.S. Pat. No. 3,342,892; Borman, U.S. Pat. No. 3,344,116; Hori et al., U.S. Pat. No. 3,384,619; Faurote et al, U.S. Pat. No. 3,440,217; and Cooper et al., U.S. Pat. Nos. 3,661,848, 3,733,299, 3,838,102, and 3,988,297. Disclosures relating to metal based catalysts which do not include amines, are known from patents such as Wieden et al., U.S. Pat. No. 3,442,885 (copper-amidines); Nakashio et al., U.S. Pat. No. 3,573,257 (metal-alcholate or -phenolate); Kobyashi et al., U.S. Pat. No. 3,445,880 (cobalt chelates); and the like. In the Stamatoff patent, the polyphenylene ethers are produced by reacting the corresponding phenolate ion with an initiator, such as peroxy acid salt, and acid peroxide, a hypohalite, and the like, in the presence of a complexing agent. Disclosures relating to non-catalytic processes, such as oxidation with lead oxide, silver oxide, etc., are described in Price et al., U.S. Pat. No. 3,383,212. Cizek, U.S. Pat. No. 3,383,435 discloses polyphenylene ether-styrene resin compositions. All of the above-mentioned disclosures are incorporated by reference.
In the prior art, rubber-modified styrene resins have been admixed with polyphenylene ether resins to form compositions that have modified properties. The Cizek patent, U.S. Pat. No. 3,383,435, discloses rubber-modified styrene resin-polyphenylene ether resin compositions wherein the rubber component is of the unsaturated type such as polymers and copolymers of butadiene. The physical properties of these compositions are such that it appears that many of the properties of the styrene resins have been upgraded, while the moldability of the polyphenylene ethers are improved.
Hindered phenols have been employed as oxidation stabilizers for materials such as hydrocarbons, rubbers, polyolefins, and the like. Some of the advantages claimed are a reduction in the initial color or in the rate of oxygen absorption or carbonyl generation at high temperatures, and better retention of impact strength upon heat-aging. For example, Yamanouchi et al., U.S. Pat. No. 3,700,750, which is incorporated herein by reference, discloses the use of certain sterically hindered phenols in polyphenylene oxide compositions.
It has now been found that a composition of a polyphenylene ether resin, a rubber modified alkenyl aromatic resin, and a hindered tris-phenol, is a very useful thermoplastic molding material having good thermal oxidative stability and improved impact strength.
It is, therefore, a primary object of this invention to provide improved compositions that are based on polyphenylene ether resins, modified alkenyl aromatic resins, and hindered tris-phenols.
Another object of this invention is to provide molding compositions and molded articles that are based on a polyphenylene ether resin, a rubber modified alkenyl aromatic resin, and a hindered tris-phenol and that overall have slightly improved thermal oxidative stability.
Still another object of this invention is to provide molding compositions and molded articles that are based on a polyphenylene ether resin, a rubber modified alkenyl aromatic resin and a hindered tris-phenol and that have greatly improved impact strength.
It is also an object of this invention to provide the above-described, improved molding compositions in reinforced and/or flame-retardant embodiments.